Project Summary: Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease characterized by progressive motor neuron loss, paralysis and death within 2 to 5 years of diagnosis. Currently, no effective pharmacological agents exist for the treatment of this devastating disease. Neuroinflammation may greatly influence the progression of motor neuron loss during ALS. Cannabinoids produce anti-inflammatory actions via CB1 and CB2 receptors and delay the progression of pathologic conditions characterized by neuroinflammation. In G93A-SOD1 (G93A) mutant mice, the most well-characterized animal model of ALS, we demonstrate that mRNA, receptor binding and function of CB2, but not CB1, receptors are dramatically and selectively upregulated in the spinal cords of G93A mice in a temporal pattern closely paralleling disease progression. More importantly, daily injections of two structurally diverse selective CB2 agonists (AM-1241 and L- 759,633) initiated at symptom onset, markedly maintain motor function and increase the survival interval after disease onset. Therefore, we propose that selective CB2 agonists may represent a novel therapeutic modality for ALS. While CB2 agonists may prove useful for this devastating neurodegenerative disease, their development as pharmaceutical agents has been fundamentally hindered by their relative insolubility in aqueous, or other biocompatible, vehicles. Indeed, several lines of evidence indicate that the actual maximal efficacy of AM-1241 might have been underestimated due to less than optimal drug delivery by the vehicle employed in our preliminary studies. As such, we propose that pharmacokinetic studies are needed to determine the most efficient vehicle, route of administration and/or dose required to produce the maximal efficacy of AM-1241 in G93A mice. The current A1 revision of this R21 application will "identify candidate therapeutics" and "obtain preliminary data on the efficacy of candidate therapeutics" for ALS by conducting the following two Specific Aims: Specific Aim 1 will identify novel CB2 agonists as candidate therapeutics for ALS by screening a series of indole and classic cannabinoid-based CB2 agonists provided by Dr. John W. Huffman (Clemson University, SC) for their ability to slow disease progression and prolong survival of G93A mice. Specific Aim 2 will optimize the therapeutic potential of AM-1241, a CB2 agonist with proven efficacy in the G93A mouse model of ALS. This will be accomplished by employing the vehicle and route of administration demonstrated by pharmacokinetic studies to produce the greatest delivery of AM-1241 to serum and spinal cords. Selective CB2 agonists identified by this project could be the first efficacious drugs for the management of ALS. Most importantly, our long-term goal is to translate results from these studies into a future clinical trial in ALS patients. Project Narrative: Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease characterized by progressive motor neuron loss, paralysis and death within 2 to 5 years of diagnosis. Currently, no effective drugs exist for the treatment of this devastating disease. Based on some exciting preliminary evidence, this project will seek to discover new drugs called "CB2 agonists" that could be the first class of effective drugs to prolong the lives of ALS patients.